Synthesis method of 9-bromoanthracene

Abstract

The invention discloses a synthesis method of 9-bromoanthracene, and belongs to the technical field of organic synthesis. According to the method, anthracene is used as a raw material, inorganic bromine salt is used as a bromine source, hydrogen peroxide is used as an oxidizing agent, and 9-bromoanthracene is synthesized in a mixed solvent in a high-selectivity manner under the catalysis of composite Lewis acid; and purifying the crude product through stepped step-by-step recrystallization to obtain a high-purity product. Through the synergistic effect of the composite catalytic system and the mixed solvent, generation of a 9, 10-dibromoanthracene byproduct difficult to remove is inhibited from the source, and efficient separation of the product and key impurities can be realized without column chromatography in combination with a gradient cooling fractional crystallization process. The method is green and safe in process, simple to operate, low in cost and easy to industrialize, and the prepared 9-bromoanthracene can meet the application requirements of OLED photoelectric materials and other high-end fields.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for synthesizing 9-bromoanthracene. Background Technology

[0002] 9-Bromoanthracene is a highly reactive polycyclic aromatic hydrocarbon functional intermediate. Due to the excellent conjugated photoelectric properties of the anthracene ring and the flexible modifiability of the bromine atom at the 9-position, it is widely used in various fields such as organic optoelectronic materials, pharmaceutical intermediates, and functional dye synthesis. Especially in the organic light-emitting diode (OLED) industry, 9-Bromoanthracene is a core raw material for synthesizing blue light host materials, hole transport materials, and functional additives for the light-emitting layer. It is an indispensable key basic chemical in the new display and flexible electronics industry chain. In recent years, with the rapid development of the global OLED display, automotive electronics, and wearable device industries, the market demand for high-purity 9-Bromoanthracene has continued to rise. At the same time, downstream high-end applications have placed more stringent requirements on product quality, which has also posed greater challenges to the synthesis process and purification technology of 9-Bromoanthracene.

[0003] Currently, the industry has developed a variety of technical routes for the synthesis and preparation of 9-bromoanthracene. Among them, the most widely used is the electrophilic bromination reaction route with anthracene as the starting material. The mainstream processes include direct bromination with liquid bromine, bromination with N-bromosuccinimide (NBS), and various improved oxidative bromination processes. Direct bromination with liquid bromine is the earliest traditional process to achieve industrial application. It achieves 9-position bromination through a direct electrophilic substitution reaction between liquid bromine and anthracene. This method is characterized by its short route and readily available raw materials, and is currently the basic production process adopted by most chemical companies. To avoid the highly toxic and corrosive nature of liquid bromine, the industry has developed a mild bromination process using NBS as the bromine source, significantly reducing operational safety risks and becoming the mainstream method for preparing 9-bromoanthracene in the laboratory. With the advancement of green chemistry concepts, oxidative bromination processes using inorganic bromine salts as the bromine source and various oxidants as the activation system have become a research hotspot. This type of process completely eliminates the use of elemental bromine, achieving the bromination reaction by generating active bromine species in situ through oxidants, significantly improving environmental friendliness and operational safety. For the purification of 9-bromoanthracene, the industry mainly uses recrystallization and column chromatography. Column chromatography is mostly used for preparing high-purity samples in the laboratory, while recrystallization is the only feasible purification method in industrial production.

[0004] Although existing technologies have established relatively complete synthesis and purification routes, there are still many technical defects and industry pain points that cannot be addressed simultaneously in actual industrial production and high-end application adaptation. First, the traditional direct bromination method of liquid bromine poses serious safety and environmental hazards. Liquid bromine is highly toxic, volatile, and corrosive, requiring extremely high corrosion resistance and sealing of production equipment. It also carries a high risk of leakage during operation and produces a large amount of highly toxic hydrogen bromide tail gas, resulting in high environmental treatment costs. Furthermore, the process exhibits extremely poor reaction selectivity, with minimal difference in reactivity between the 9 and 10 positions of the anthracene ring, readily generating the 9,10-dibromoanthracene byproduct. This byproduct is structurally highly homologous to the main product and has extremely similar physicochemical properties, making it difficult to remove using conventional methods. Even after multiple recrystallizations, it is impossible to reduce the byproduct to below the threshold required for OLED applications, leading to significant losses in product yield. Secondly, the NBS bromination method and existing improved oxidative bromination processes still face bottlenecks in industrialization. The NBS bromination method has high bromine source costs, and the reaction process inevitably generates dibromo byproducts. After scaling up production, the purity and yield of the product will decrease significantly, resulting in extremely poor industrial economics. Moreover, the published oxidative bromination patent technologies mostly use high-valent iodine compounds as oxidants, which not only have expensive reagent prices and large quantities, significantly increasing raw material costs, but also generate a large amount of organic solid waste. At the same time, they generally use carbon tetrachloride, which is strictly controlled under the Montreal Protocol, as the reaction solvent, resulting in poor environmental compliance and making it impossible to achieve large-scale continuous production. Some processes also require complex operations such as low-temperature controlled feeding and multi-stage gradient heating, which places high demands on production equipment and makes it difficult to guarantee batch stability. Furthermore, existing purification processes have significant technical bottlenecks. Conventional single-solvent recrystallization cannot effectively separate 9-bromoanthracene from 9,10-dibromoanthracene, and multiple recrystallizations lead to a sharp drop in product yield. Column chromatography is not suitable for continuous industrial production and generates a large amount of waste silica gel and organic solvents, further exacerbating environmental pressures. Ultimately, existing processes cannot simultaneously achieve high purity, high yield, low cost, green safety, and industrial adaptability, making it difficult to meet the large-scale supply demand of the downstream OLED industry for ultra-high purity 9-bromoanthracene. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for synthesizing 9-bromoanthracene.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a method for synthesizing 9-bromoanthracene, comprising the following steps: (1) Under the protection of an inert gas, anthracene, inorganic bromide and complex Lewis acid are added to a mixed solvent and stirred evenly. The temperature is controlled at 25℃-45℃, and hydrogen peroxide aqueous solution is slowly added dropwise. The temperature fluctuation during the dropwise addition does not exceed ±2℃. After the dropwise addition is completed, the mixture is kept warm and stirred for 3h-6h. (2) After the reaction is completed, add saturated sodium sulfite aqueous solution to the reaction system to quench excess hydrogen peroxide, stir for 15 min-30 min and let stand to separate the layers, separate the organic phase, extract the aqueous phase 1-2 times with extraction solvent, combine the organic phases, wash with saturated brine until neutral, dry with anhydrous desiccant, concentrate under reduced pressure to remove solvent, and obtain crude 9-bromoanthracene. (3) After purifying the crude 9-bromoanthracene according to the purification process, pure 9-bromoanthracene is obtained.

[0007] Preferably, the reaction equation for the synthesis method is as follows: .

[0008] Preferably, the inorganic bromide salt refers to any one of potassium bromide, sodium bromide, or ammonium bromide.

[0009] Preferably, the composite Lewis acid refers to a composite system of a main catalyst and a co-catalyst; wherein the main catalyst is selected from any one of ferric chloride, aluminum chloride, and ferric bromide, and the co-catalyst is selected from any one of quaternary ammonium salt phase transfer catalysts and crown ether phase transfer catalysts.

[0010] Preferably, the mixed solvent refers to a mixed system of haloalkanes and alkanes; wherein the haloalkanes are selected from any one of 1,2-dichloroethane, dichloromethane, and chloroform, and the alkanes are selected from any one of cyclohexane, n-hexane, and n-heptane; the volume ratio of haloalkanes to alkanes is 2-4:1.

[0011] More preferably, the inorganic bromide salt refers to potassium bromide.

[0012] More preferably, the main catalyst of the composite Lewis acid is ferric chloride, and the co-catalyst is any one of tetrabutylammonium bromide, benzyltriethylammonium chloride, and 18-crown-6.

[0013] More preferably, the mixed solvent refers to a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1.

[0014] Preferably, the inert gas in (1) is nitrogen.

[0015] Preferably, the temperature in (1) is controlled at 30-40℃.

[0016] Preferably, the molar ratio of anthracene, inorganic bromide and hydrogen peroxide in (1) is 1:1.05-1.5:1.1-1.8.

[0017] Preferably, the molar ratio of the main catalyst and the co-catalyst in the anthracene and the composite Lewis acid in (1) is 1:0.08-0.42:0.02-0.1.

[0018] Preferably, the solid-liquid ratio of anthracene and mixed solvent in (1) is 1g:10ml-20ml.

[0019] More preferably, the molar ratio of anthracene, inorganic bromide and hydrogen peroxide in (1) is 1:1.05:1.2.

[0020] More preferably, the molar ratio of the main catalyst and the co-catalyst in the anthracene and the composite Lewis acid in (1) is 1:0.2:0.06.

[0021] More preferably, the solid-liquid ratio of anthracene and mixed solvent in (1) is 1g:15ml.

[0022] Preferably, the concentration of the hydrogen peroxide aqueous solution in (1) is 20-30 wt%.

[0023] More preferably, the concentration of the hydrogen peroxide aqueous solution in (1) is 30 wt%.

[0024] Preferably, the extraction solvent in (2) is consistent with the halohydrocarbon component in the mixed solvent, and the amount of solvent used in a single extraction is 1 / 5 to 1 / 3 of the volume of the aqueous phase to be extracted.

[0025] Preferably, the anhydrous desiccant in (2) is either anhydrous sodium sulfate or anhydrous magnesium sulfate.

[0026] More preferably, the anhydrous desiccant in (2) is anhydrous sodium sulfate.

[0027] Preferably, the purification process in (3) includes the following steps: S1. Add crude 9-bromoanthracene to a recrystallization solvent, heat to 60℃-80℃, and stir until completely dissolved to obtain a crude product solution; S2. The crude product solution is heated and filtered at 60℃-80℃ to obtain a clear filtrate; S3. Cool the clarified filtrate to 40℃-45℃ at a rate of 5℃-10℃ / h, keep it at this temperature and stir for 1h-2h, filter to remove impurities, and obtain a primary filtrate; cool the primary filtrate to 20℃-25℃ at a rate of 4℃-6℃ / h, keep it at this temperature and stir for 0.5h-1h, and then cool it to 10℃-20℃ at a rate of 2℃-3℃ / h, keep it at this temperature and stir for 2h-3h, to obtain a 9-bromoanthracene crystal slurry; S4. Centrifuge and filter the 9-bromoanthracene crystal slurry. Wash the filter cake 1-2 times with a cold recrystallization solvent at 0℃-5℃. After drying, pure 9-bromoanthracene is obtained.

[0028] Preferably, the solid-liquid ratio of crude 9-bromoanthracene to recrystallization solvent in S1 is 1g:3ml-6ml.

[0029] Preferably, the recrystallization solvent in S1 is a mixture of aromatic hydrocarbons and alcohols, with a volume ratio of aromatic hydrocarbons to alcohols of 1-3:1; the aromatic hydrocarbons are selected from toluene and xylene, and the alcohols are selected from ethanol and isopropanol.

[0030] More preferably, the aromatic hydrocarbon in the recrystallization solvent in S1 is toluene, and the alcohol is isopropanol.

[0031] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention abandons the highly toxic and corrosive liquid bromine and reaction solvents subject to strict environmental control in traditional processes. It uses inexpensive and readily available bulk inorganic bromine salts as bromine sources and industrial-grade hydrogen peroxide as a green oxidant. No highly toxic tail gas is generated during the reaction process, the amount of solid waste and wastewater discharge is greatly reduced, the operational safety risks are significantly reduced, and it fully complies with the policy requirements of green chemical industry in China and the environmental compliance standards of industrial production.

[0032] 2. This invention utilizes the synergistic effect of a composite Lewis acid catalytic system and a mixed solvent system to regulate the generation rate and reaction site targeting of active bromine species, achieving efficient anthracene conversion under mild isothermal reaction conditions. Simultaneously, it inhibits the generation of difficult-to-remove byproducts of 9,10-dibromoanthracene from the source of the reaction, solving the core industry pain points of poor selectivity, numerous byproducts, and difficult subsequent purification in traditional bromination processes.

[0033] 3. This invention develops a stepwise recrystallization purification process that eliminates the need for non-industrializable purification methods such as column chromatography. It achieves efficient separation of the main product and key impurities through a single recrystallization step, avoiding product loss caused by multiple recrystallizations in traditional methods. The purification yield is high, the operation process is simple, and it can be directly adapted to industrial continuous production, significantly shortening the production cycle and improving production efficiency.

[0034] 4. The synthesis and purification processes of this invention both adopt conventional chemical unit operations, without the need for special conditions such as low temperature control, high pressure reaction, and precision photo / electrocatalytic equipment. Traditional chemical reactors and crystallization vessels can be used to achieve the entire process production. The process window is wide, the parameter tolerance is strong, the product quality stability between batches is excellent, the solvent can be recycled and reused, and the overall production cost is significantly reduced compared with the existing process, which has strong industrial applicability.

[0035] 5. The 9-bromoanthracene product prepared by this invention has high purity and extremely low residual amount of key impurities, which can meet the stringent quality requirements of downstream OLED optoelectronic materials, high-end pharmaceutical intermediates and other fields. It solves the problem that the quality of existing process products cannot be adapted to high-end application scenarios, and the product has significant market competitiveness and application value. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0037] Example 1: A specific method for synthesizing 9-bromoanthracene, comprising the following steps: (1) Under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.0105 mol potassium bromide, 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide were added to 26.7 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred until homogeneous, and the temperature was controlled at 30 °C. 1.36 g of 30 wt% hydrogen peroxide aqueous solution (0.012 mol) was slowly added dropwise. The temperature fluctuation during the dropwise addition should not exceed ±2 °C. After the dropwise addition was completed, the mixture was kept at the temperature and stirred for 3 h. (2) After the reaction is completed, saturated sodium sulfite aqueous solution is added to the reaction system to quench excess hydrogen peroxide. After stirring for 15 min, the mixture is allowed to stand and separate into layers. The organic phase is separated and the aqueous phase is extracted once with 1,2-dichloroethane. The amount of solvent used in each extraction is 1 / 5 of the volume of the aqueous phase to be extracted. The organic phases are combined, washed with saturated brine until neutral, dried with anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent, to obtain crude 9-bromoanthracene. (3.1) Add 2g of crude 9-bromoanthracene to 6ml of recrystallization solvent (a mixture of toluene and isopropanol in a volume ratio of 1:1), heat to 60℃, and stir until completely dissolved to obtain a crude product solution; (3.2) The crude solution was heated and filtered at 60°C to obtain a clear filtrate; (3.3) Cool the clarified filtrate to 40°C at a rate of 5°C / h, keep it warm and stir for 1h, filter to remove impurities, and obtain a primary filtrate; cool the primary filtrate to 20°C at a rate of 4°C / h, keep it warm and stir for 0.5h, then cool it to 10°C at a rate of 2°C / h, keep it warm and stir for 2h, and obtain 9-bromoanthracene crystal slurry; (3.4) Centrifuge and filter the 9-bromoanthracene crystal slurry. Wash the filter cake once with a cold recrystallization solvent at 0℃-5℃. After drying, pure 9-bromoanthracene is obtained.

[0038] Example 2: A specific method for synthesizing 9-bromoanthracene, comprising the following steps: (1) Under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.0105 mol potassium bromide, 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide were added to 26.7 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred until homogeneous, and the temperature was controlled at 35 °C. 1.36 g of 30 wt% hydrogen peroxide aqueous solution (0.012 mol) was slowly added dropwise. The temperature fluctuation during the dropwise addition should not exceed ±2 °C. After the dropwise addition was completed, the mixture was kept at the temperature and stirred for 4 h. (2) After the reaction is completed, saturated sodium sulfite aqueous solution is added to the reaction system to quench excess hydrogen peroxide. After stirring for 20 min, the mixture is allowed to stand and separate into layers. The organic phase is separated and the aqueous phase is extracted twice with 1,2-dichloroethane. The amount of solvent used in each extraction is 1 / 4 of the volume of the aqueous phase to be extracted. The organic phases are combined, washed with saturated brine until neutral, dried with anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent, to obtain crude 9-bromoanthracene. (3.1) Add 2g of crude 9-bromoanthracene to 10ml of recrystallization solvent (a mixture of toluene and isopropanol in a volume ratio of 2:1), heat to 70℃, and stir until completely dissolved to obtain a crude product solution; (3.2) The crude solution was heated and filtered at 70°C to obtain a clear filtrate; (3.3) Cool the clarified filtrate to 42°C at a rate of 8°C / h, keep it warm and stir for 1.5h, filter to remove impurities, and obtain a primary filtrate; cool the primary filtrate to 22°C at a rate of 5°C / h, keep it warm and stir for 0.8h, and then cool it to 15°C at a rate of 2.5°C / h, keep it warm and stir for 2.5h, to obtain 9-bromoanthracene crystal slurry; (3.4) The 9-bromoanthracene crystal slurry was centrifuged and filtered. The filter cake was washed twice with a cold recrystallization solvent at 0℃-5℃, and dried to obtain pure 9-bromoanthracene; NMR was [missing value]. 1 HNMR(CDCl3): δ8.64-8.60(m,2H),8.43(s,1H),8.01-7.93(m,2H),7.62-7.58(m,2H),7.55-7.49(m,2H).

[0039] Example 3: A specific method for synthesizing 9-bromoanthracene, comprising the following steps: (1) Under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.0105 mol potassium bromide, 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide were added to 26.7 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred until homogeneous, and the temperature was controlled at 40 °C. 1.36 g of 30 wt% hydrogen peroxide aqueous solution (0.012 mol) was slowly added dropwise. The temperature fluctuation during the dropwise addition should not exceed ±2 °C. After the dropwise addition was completed, the mixture was kept at the temperature and stirred for 6 h. (2) After the reaction is completed, saturated sodium sulfite aqueous solution is added to the reaction system to quench excess hydrogen peroxide. After stirring for 30 min, the mixture is allowed to stand and separate into layers. The organic phase is separated and the aqueous phase is extracted twice with 1,2-dichloroethane. The amount of solvent used in each extraction is 1 / 3 of the volume of the aqueous phase to be extracted. The organic phases are combined, washed with saturated brine until neutral, dried with anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent, to obtain crude 9-bromoanthracene. (3.1) Add 2g of crude 9-bromoanthracene to 12ml of recrystallization solvent (a mixture of toluene and isopropanol in a volume ratio of 3:1), heat to 80℃, and stir until completely dissolved to obtain a crude product solution; (3.2) The crude solution was heated and filtered at 80°C to obtain a clear filtrate; (3.3) Cool the clarified filtrate to 45°C at a rate of 10°C / h, keep it warm and stir for 2h, filter to remove impurities, and obtain a primary filtrate; cool the primary filtrate to 25°C at a rate of 6°C / h, keep it warm and stir for 1h, then cool it to 20°C at a rate of 3°C / h, keep it warm and stir for 3h, and obtain 9-bromoanthracene crystal slurry; (3.4) Centrifuge and filter the 9-bromoanthracene crystal slurry. Wash the filter cake twice with a cold recrystallization solvent at 0℃-5℃. After drying, pure 9-bromoanthracene is obtained.

[0040] Example 4: The difference between Example 4 and Example 2 is that potassium bromide is replaced with sodium bromide.

[0041] Example 5: The difference between Example 5 and Example 2 is that potassium bromide is replaced with ammonium bromide.

[0042] Example 6: The difference between Example 6 and Example 2 is that 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide are replaced with 0.002 mol ferric chloride and 0.0006 mol benzyltriethylammonium chloride.

[0043] Example 7: The difference between Example 7 and Example 2 is that 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide are replaced with 0.002 mol ferric chloride and 0.0006 mol 18-crown-6.

[0044] Example 8: The difference between Example 8 and Example 2 is that 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide are replaced with 0.002 mol aluminum chloride and 0.0006 mol tetrabutylammonium bromide.

[0045] Example 9: The difference between Example 9 and Example 2 is that 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide are replaced with 0.002 mol ferric bromide and 0.0006 mol tetrabutylammonium bromide.

[0046] Example 10: The difference between Example 10 and Example 2 is that the mixed solvent is replaced by a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1 with a mixture of dichloromethane and n-hexane in a volume ratio of 3:1.

[0047] Example 11: The difference between Example 11 and Example 2 is that the mixed solvent is replaced by a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1 with a mixture of chloroform and n-heptane in a volume ratio of 3:1.

[0048] Example 12: The difference between Example 12 and Example 2 is that (1) the temperature control is changed to 25℃.

[0049] Example 13: The difference between Example 13 and Example 2 is that (1) the temperature control is changed to 45℃.

[0050] Example 14: The difference between Example 14 and Example 2 is that: in (1), "under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.0105 mol potassium bromide, 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide were added to 26.7 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred evenly, and the temperature was controlled at 35°C. 1.36 g was then slowly added dropwise." The original text was revised to read: "Under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.0125 mol potassium bromide, 0.0008 mol ferric chloride and 0.0002 mol tetrabutylammonium bromide were added to 17.8 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred until homogeneous, and the temperature was controlled at 35 ℃. 1.25 g of 30 wt% hydrogen peroxide aqueous solution (0.011 mol) was slowly added dropwise, with the temperature fluctuation not exceeding ±2 ℃ during the dropwise addition. After the dropwise addition was completed, the mixture was kept at the temperature and stirred for 4 h."

[0051] Example 15: The difference between Example 14 and Example 2 is that: in (1), "under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.0105 mol potassium bromide, 0.002 mol ferric chloride and 0.0006 mol tetrabutylammonium bromide were added to 26.7 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred evenly, and the temperature was controlled at 35°C. 1.36 g was then slowly added dropwise." The original text was revised to read: "Under nitrogen protection, 0.01 mol (1.78 g) anthracene, 0.015 mol potassium bromide, 0.0042 mol ferric chloride and 0.001 mol tetrabutylammonium bromide were added to 35.6 ml of mixed solvent (a mixture of 1,2-dichloroethane and cyclohexane in a volume ratio of 3:1), stirred until homogeneous, and the temperature was controlled at 35 ℃. 2.04 g of 30 wt% hydrogen peroxide aqueous solution (0.012 mol) was slowly added dropwise, with the temperature fluctuation not exceeding ±2 ℃ during the dropwise addition. After the dropwise addition was completed, the mixture was kept at the temperature and stirred for 4 hours."

[0052] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 uses the direct bromination method of liquid bromine in the existing process. The specific preparation method is as follows: (1) Add 0.01mol (1.78g) anthracene and 26.7ml carbon tetrachloride to a three-necked flask, stir well, control the temperature at 0℃, and add 0.0105mol (1.68g) liquid bromine dropwise, and control the temperature fluctuation to not exceed ±2℃ throughout the process; (2) After the addition is complete, heat to the reflux temperature and stir for 2 hours. Monitor the reaction by TLC to ensure complete conversion of the raw materials. (3) After the reaction was completed, saturated sodium sulfite aqueous solution was added to quench the excess liquid bromine. After stirring for 20 min, the mixture was allowed to stand and separate into layers. The organic phase was separated and the aqueous phase was extracted twice with carbon tetrachloride. The amount of each extraction was 1 / 4 of the volume of the aqueous phase. The organic phases were combined, washed with saturated brine until neutral, dried with anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent, to obtain crude 9-bromoanthracene. (4) The crude product was purified using conventional existing technology: recrystallized three times with anhydrous ethanol at a solid-liquid ratio of 1g:8ml. Each time, the temperature was raised to reflux and dissolved, and then cooled to 0℃ and kept warm for 2h. After filtration and drying, pure 9-bromoanthracene was obtained.

[0053] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 follows the synthesis and purification method in Chinese CN115872832B.

[0054] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that tetrabutylammonium bromide is not added.

[0055] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the mixed solvent is replaced with 1,2-dichloroethane.

[0056] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the mixed solvent is replaced with cyclohexane.

[0057] Performance testing: The crude 9-bromoanthracene and the purified 9-bromoanthracene obtained according to the synthesis methods in Examples 1-15 and Comparative Examples 1-5 were subjected to performance tests under the following conditions: (1) GC detection conditions Instrument: Agilent 7890A; Chromatographic column: HP-5 capillary column (30m×0.32mm×0.25μm); Inlet temperature: 280℃; Detector temperature: 300℃ (FID flame ionization detector); Programmed temperature rise: Initial temperature 80℃, hold for 2 min, then increase to 280℃ at 15℃ / min, hold for 10 min; Carrier gas: high-purity nitrogen, flow rate 1.0 mL / min; injection volume 1 μL; split ratio 50:1; Quantitative method: Area normalization method.

[0058] (2) HPLC detection conditions Instrument: Agilent 1260 Infinity II; Chromatographic column: Agilent Eclipse Plus C18 column (250mm×4.6mm×5μm); Mobile phase: methanol:water = 95:5 (V / V); Flow rate: 1.0 mL / min; Column temperature: 30℃; Detection wavelength: 254nm; Injection volume: 10μL; Run time: 20min; Quantitative method: Area normalization method.

[0059] Calculation method: Molar yield: Based on the amount of anthracene feedstock, the calculation formula is as follows: molar yield = ; Purity and impurity content: Calculated using the chromatographic peak area normalization method, which is the percentage of the peak area of ​​the target component / impurity component to the total peak area.

[0060] The test results are shown in Table 1.

[0061] Table 1 Performance Test Results

[0062] Data Analysis: All embodiments of this invention exhibit excellent conversion rates and selectivity in their synthesis reactions. The GC purity of the crude product is consistently above 97.64%, and the content of the byproduct 9,10-dibromoanthracene is controlled below 0.52%. The optimal embodiment 2 achieves a crude product GC purity of 98.76% and a 9,10-dibromoanthracene content of only 0.32%. From the perspective of the reaction's essence, the 9 and 10 positions of the anthracene ring are the sites with the highest π electron cloud density in the conjugated system and are also the dominant active sites for electrophilic substitution reactions. Furthermore, the reactivity difference between the two sites is minimal. The core challenge of traditional bromination processes is the inability to control the generation rate and concentration of active bromine species. After monobromination at the 9 position, secondary bromination at the 10 position is easily and rapidly observed, generating the difficult-to-remove 9,10-dibromoanthracene byproduct. This invention solves this industry pain point through the synergistic effect of a composite Lewis acid catalytic system and a haloalkane-alkane mixed solvent system: in the composite Lewis acid, the main catalyst Lewis acid can specifically coordinate with the π electrons at the 9 position of the anthracene ring, further directionally increasing the electron cloud density at the 9 position. This enhances the site targeting of electrophilic substitution, while the co-catalyst phase transfer agent can construct a continuous ion transport channel in the water-oil two-phase system, continuously and uniformly transferring bromide ions and hydrogen peroxide from the aqueous phase to the reaction site in the organic phase. This completely avoids the sudden increase in local active bromine concentration caused by the traditional two-phase reaction only occurring at the interface, and achieves the controlled and sustained release of active bromine species. At the same time, the mixed solvent system composed of haloalkanes and alkanes can match the kinetic requirements of the reaction by adjusting the volume ratio. This ensures the good solubility of the substrate anthracene and Lewis acid catalyst in the organic phase, providing a homogeneous environment for the complete reaction, while avoiding the problem of excessively rapid active bromine formation rate caused by a highly polar single solvent.

[0063] The performance of each comparative example was significantly inferior to that of the embodiments of the present invention. Comparative Example 1 used a traditional direct bromination process with liquid bromine, and its crude product had a GC purity of only 96.23% and a 9,10-dibromoanthracene content as high as 2.17%. Even after three recrystallizations with anhydrous ethanol, the purity of the finished product was only 98.51%, with a dibromoanthracene residue of 1.12% and a total yield of only 72.14%. From the reaction mechanism, liquid bromine, as a strongly electrophilic bromine source, will rapidly dissociate in the system to generate a high concentration of bromine ions. The activity difference between the 9 and 10 positions of the anthracene ring is extremely small, and the high concentration of active bromine species will instantly trigger the dibromine ion at the 10 position after the substitution at the 9 position. Hypobromination cannot achieve selective control of monobromination at all. At the same time, the high volatility of liquid bromine leads to a severe uneven distribution of bromine concentration in the system, which further aggravates the formation of by-products. In the purification process, 9-bromoanthracene and 9,10-dibromoanthracene have highly homologous core structures and have very little difference in solubility in a single ethanol solvent. Traditional one-time cooling recrystallization will cause the two to form a eutectic, and the impurities will be permanently encapsulated in the product lattice. Even if recrystallization is repeated, it cannot be effectively removed and will also cause a large loss of product, ultimately resulting in low purity and low yield. Comparative Example 2, using the process described in patent CN115872832B, yielded a crude product with a 9,10-dibromoanthracene content of 0.68%, a finished product purity of 99.23%, and a total yield of 81.73%, which is lower than the optimal embodiment of this invention. The defects may be due to design flaws in the oxidation and catalysis system. This process uses a high-valent iodine compound as the main oxidant, which has strong and uncontrollable oxidizing activity, leading to the rapid and concentrated oxidation of bromide ions into active bromine, making it impossible to achieve uniform and slow release. At the same time, the amount of Lewis acid ferric chloride used is as high as 2.5 equivalents, far exceeding the amount used in the catalytic stage of this invention. Excessive Lewis acid not only exacerbates the oxidation side reactions and over-bromination of anthracene rings but also generates a large amount of iron-containing solid waste. In addition, this process uses carbon tetrachloride, which is subject to strict environmental regulations, as a solvent. Its strong polarity further amplifies the risk of side reactions. The column chromatography process used in the purification stage not only cannot achieve continuous industrial production but also causes irreversible product loss, ultimately failing to achieve the impurity control and high yield of this invention.Comparative Example 3 only removed the phase transfer co-catalyst tetrabutylammonium bromide from the complex Lewis acid. Its crude product purity plummeted to 82.34%, the 9,10-dibromoanthracene content increased to 1.85%, and the total yield was only 65.32%. This result directly confirms the core role of the phase transfer co-catalyst in this reaction system. This reaction is a typical water-oil two-phase reaction. The substrate anthracene and the Lewis acid main catalyst are located in the organic phase, while the bromine source potassium bromide and the oxidant hydrogen peroxide are located in the aqueous phase. There is a natural mass transfer barrier between the two, and they can only react at the interface between the two phases. Without the phase transfer agent, bromide ions and oxidant cannot enter the organic phase bulk. The reaction can only occur at a limited interface, resulting in an extremely slow overall reaction rate. The raw material anthracene cannot be completely converted, and a large amount of unreacted raw material remains in the crude product, resulting in a significant decrease in purity. At the same time, local enrichment of active bromine species occurs at the interface, with a concentration far exceeding the requirements of the monobromination reaction, which rapidly triggers secondary bromination at the 10 position. Ultimately, the reaction shows a decrease in both conversion rate and selectivity. In Comparative Example 4, the mixed solvent was replaced with a single 1,2-dichloroethane. The content of the crude 9,10-dibromoanthracene increased to 2.03%, the purity of the finished product was only 99.05%, and the overall yield was 78.42%. The core reason is the direct control effect of solvent polarity on reaction selectivity. 1,2-Dichloroethane is a moderately polar haloalkane, which has a strong solvation effect on Lewis acids and will significantly enhance the catalytic activity of Lewis acids. This leads to a significant acceleration in the rate of hydrogenation of bromide ions by peroxide, and the concentration of active bromine species in the system increases rapidly, breaking the kinetic equilibrium of the monobromination reaction. After the anthracene ring is brominated at the 9-position, it undergoes rapid secondary bromination. The content of by-products is close to that of the traditional liquid bromination method. Even with the purification process of this invention, it is impossible to reduce the impurity residue to the level of the embodiments of this invention. At the same time, excessive by-products will lead to increased product loss during the purification process and a significant decrease in the overall yield. Comparative Example 5, where the mixed solvent was replaced with cyclohexane, yielded a crude product purity of only 61.52% and an overall yield of 42.63%, which is completely unsuitable for industrial application. The core issue stems from the solvent's severely insufficient solubility for the substrate and catalyst. Cyclohexane, a strong nonpolar alkane solvent, exhibits extremely poor solubility for polar Lewis acid catalysts and phase transfer reagents. The catalyst cannot be uniformly dispersed in the system, with most existing in aggregated form and losing catalytic activity. Consequently, the main reaction of hydrogen peroxide oxidizing bromide ions is almost impossible to occur, resulting in a low conversion rate of the anthracene feedstock. A large amount of unreacted feedstock remains in the crude product. Furthermore, the nonpolar solvent has a weak solvation effect on the anthracene ring, and the electrophilic activity at the 9-position of the anthracene ring cannot be effectively activated. The reaction kinetics are severely inadequate, and even extending the reaction time cannot achieve complete conversion of the feedstock, ultimately leading to a precipitous drop in purity and yield.

[0064] All embodiments of this invention achieve a finished product HPLC purity ≥99.87% and 9,10-dibromoanthracene residue ≤0.07% through a single step-by-step recrystallization process. The optimal embodiment 2 achieves a finished product purity of 99.94% and a dibromoanthracene residue of only 0.02%, far superior to the purification effects of multiple recrystallizations in Comparative Example 1 and column chromatography in Comparative Example 2. This solves the technical pain point in the industry that "9,10-dibromoanthracene cannot be effectively removed by recrystallization," its core stemming from the precise control of crystallization thermodynamics and kinetics. The molecular structures of 9-bromoanthracene and 9,10-dibromoanthracene differ by only one bromine atom. Their lattice energies, intermolecular van der Waals forces, and π-π stacking interactions are highly similar, and their solubility curves in a single solvent almost completely overlap. Traditional single-step cooling recrystallization leads to both reaching a supersaturated state simultaneously, forming a eutectic encapsulation, making effective separation impossible. This is the core reason why multiple recrystallizations in existing technologies still fail to remove this impurity. This invention employs a mixed recrystallization solvent of aromatic hydrocarbons and alcohols. By controlling the polarity and hydrogen bonding of the solvents, the solubility difference between the two is precisely amplified: aromatic hydrocarbons such as toluene and xylene can specifically bind to the anthracene ring through π-π interactions, significantly increasing the solubility of 9-bromoanthracene. Meanwhile, protic alcohol solvents such as ethanol and isopropanol can significantly reduce the solubility of 9,10-dibromoanthracene, which has higher symmetry, through polarity control. This results in a significant solubility difference between the two in the mid-temperature range of 40-45℃. At this temperature, 9,10-dibromoanthracene has reached a supersaturated state, while 9-bromoanthracene remains completely dissolved in the system, creating a thermodynamic basis for stepwise impurity removal. Based on this, the step-by-step cooling process of the present invention first cools to 40-45℃ at a rate of 5-10℃ / h and holds at that temperature to promote crystal growth, allowing 9,10-dibromoanthracene to preferentially and directionally nucleate and precipitate. Impurities are completely removed from the system by filtration, thus completely avoiding the risk of eutectic crystallization in the subsequent crystallization process of the main product. Then, the temperature is gradually reduced to 10-20℃, allowing 9-bromoanthracene to precipitate slowly and uniformly, forming needle-like crystals with regular crystal shapes, free of fine powder and agglomerates. This not only achieves ultra-high product purity at the OLED level, but also ensures a single-step purification yield of ≥90% and a total yield of over 84% throughout the entire process, achieving a balance between high purity and high yield.

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing 9-bromoanthracene, characterized in that, Includes the following steps: (1) Under the protection of an inert gas, anthracene, inorganic bromide and complex Lewis acid are added to a mixed solvent and stirred evenly. The temperature is controlled at 25℃-45℃, and hydrogen peroxide aqueous solution is slowly added dropwise. The temperature fluctuation during the dropwise addition does not exceed ±2℃. After the dropwise addition is completed, the mixture is kept warm and stirred for 3h-6h. (2) After the reaction is completed, add saturated sodium sulfite aqueous solution to the reaction system to quench excess hydrogen peroxide, stir for 15 min-30 min and let stand to separate the layers, separate the organic phase, extract the aqueous phase 1-2 times with extraction solvent, combine the organic phases, wash with saturated brine until neutral, dry with anhydrous desiccant, concentrate under reduced pressure to remove solvent, and obtain crude 9-bromoanthracene. (3) After purifying the crude 9-bromoanthracene according to the purification process, pure 9-bromoanthracene is obtained; The inorganic bromide salt refers to any one of potassium bromide, sodium bromide, or ammonium bromide. The composite Lewis acid refers to a composite system of a main catalyst and a co-catalyst; wherein the main catalyst is selected from any one of ferric chloride, aluminum chloride, and ferric bromide, and the co-catalyst is selected from any one of quaternary ammonium salt phase transfer catalysts and crown ether phase transfer catalysts; The mixed solvent refers to a mixed system of halogenated hydrocarbons and alkanes; wherein the halogenated hydrocarbons are selected from any one of 1,2-dichloroethane, dichloromethane, and trichloromethane, and the alkanes are selected from any one of cyclohexane, n-hexane, and n-heptane; the volume ratio of halogenated hydrocarbons to alkanes is 2-4:

1.

2. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, The inorganic bromide salt refers to potassium bromide; the main catalyst of the composite Lewis acid is ferric chloride, and the co-catalyst is any one of tetrabutylammonium bromide, benzyltriethylammonium chloride, and 18-crown-6.

3. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, The inert gas in (1) is nitrogen; the temperature is controlled at 30-40℃.

4. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, In (1), the molar ratio of anthracene, inorganic bromide, and hydrogen peroxide is 1:1.05-1.5:1.1-1.8; the molar ratio of the main catalyst and the co-catalyst in anthracene and the composite Lewis acid is 1:0.08-0.42:0.02-0.1; and the solid-liquid ratio of anthracene and the mixed solvent is 1g:10ml-20ml.

5. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, The concentration of the hydrogen peroxide aqueous solution in (1) is 20-30 wt%.

6. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, In step (2), the extraction solvent is the same as the halogenated hydrocarbon component in the mixed solvent, and the amount of solvent used in a single extraction is 1 / 5 to 1 / 3 of the volume of the aqueous phase to be extracted.

7. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, The anhydrous desiccant in (2) is either anhydrous sodium sulfate or anhydrous magnesium sulfate.

8. The method for synthesizing 9-bromoanthracene according to claim 1, characterized in that, The purification process in (3) includes the following steps: S1. Add crude 9-bromoanthracene to a recrystallization solvent, heat to 60℃-80℃, and stir until completely dissolved to obtain a crude product solution; S2. The crude product solution is heated and filtered at 60℃-80℃ to obtain a clear filtrate; S3. Cool the clarified filtrate to 40℃-45℃ at a rate of 5℃-10℃ / h, keep it at this temperature and stir for 1h-2h, filter to remove impurities, and obtain a primary filtrate; cool the primary filtrate to 20℃-25℃ at a rate of 4℃-6℃ / h, keep it at this temperature and stir for 0.5h-1h, and then cool it to 10℃-20℃ at a rate of 2℃-3℃ / h, keep it at this temperature and stir for 2h-3h, to obtain a 9-bromoanthracene crystal slurry; S4. Centrifuge and filter the 9-bromoanthracene crystal slurry. Wash the filter cake 1-2 times with a cold recrystallization solvent at 0℃-5℃. After drying, pure 9-bromoanthracene is obtained.

9. The method for synthesizing 9-bromoanthracene according to claim 8, characterized in that, The solid-liquid ratio of crude 9-bromoanthracene to recrystallization solvent in S1 is 1g:3ml-6ml.

10. The method for synthesizing 9-bromoanthracene according to claim 8, characterized in that, The recrystallization solvent in S1 is a mixture of aromatic hydrocarbons and alcohols, with a volume ratio of aromatic hydrocarbons to alcohols of 1-3:1; the aromatic hydrocarbons are selected from toluene and xylene, and the alcohols are selected from ethanol and isopropanol.

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